I am currently 15 years old, and I do magic all the time at school. I agree with you that some younger performers do not practice nearly enough before they start performing. I was like that untill I finally realized this point. Now I practice in front of the mirror untill I have everything down perfect. Also, about misdirection, I have worked a lot on it too and I think I'm pretty good at it now.
I, for the most part don't agree with the essay, because you have to perform in order to be a magician, you have to get used to hecklers, you have to see for yourself what works and what doesn't. If someone really wants to be a magician, they can't just study magic for years and start performing when they're older, they won't have the experience. Just because you're older, doesn't mean you will naturally be a better performer. For sleights and being able to do them without looking at your hands, it's all practice, which I will agree that many teens don't do enough. But when it comes to misdirection and audience control, it's all about experience. How will you be a good performer by the time you are 18 if you have never performed before. I will bet that if you take an 18 year old magician who have spent 5 years merely studing magic, and never performing it, and another 18 year-old, who have not studied as much, but have been actually performing for 5 years, the second one will be much better. Also, about how kids and teens not being good audiences, when you are older, you will have to perform for them anyways, if you've performed for this age group before, you will have the experience, u will know what to do. Performing at a young age in school, you will most likely fail when starting out, I did, but the important thing is to learn from the mistakes, therefore, gaining experience. Magic is a performance art, without actually performing it, how can you be good at it?
For all u young magicians out there that want to perform in school, resist the temptation to perform right after you learn a trick, and practice until you get it doen perfect. You'll probably fail here and there, never give up, learn from your mistakes and do better next time.
These are my veiws and mean no offense to the author of the essay above because I do see where he/she is coming from and respect his ideas.